When cats were genetically engineered to produce one of these factors, TRIMcyp, FIV replication was reduced.

Two male cats and one female with the genes were born and survived. The male passed the genes down to kittens of his own, which emitted a weaker glow.

Eric Poeschla, from the Mayo Clinic in Rochester, New York state, who led the study, reported in the journal Nature Methods: "One of the best things about this biomedical research is that it is aimed at benefiting both human and feline health. It can help cats as much as people."